The invention concerns actuator mechanisms and particularly actuating mechanisms having a contactless holding system means for a moving actuator element as well as the design of such a holding system.
Independently of their application, the principle of such holding systems is to keep a moving actuator in a relatively stable initial position. If this actuator is to be moved out of this relatively stable position, this is effected by the application of a force.
As an example of such a typically mechanically acting holding system, so-called snap-action switches may be quoted, in which a moving contact element is kept in a holding position by means of a spring for as long as said element is not moved beyond a particular critical position. After this critical position has been reached, the actuator follows a forcibly prescribed path, along which it is initially accelerated under the influence of the spring.
From printer technology, spring-driven print hammers are known (e.g., from Deutsche Offenlegungsschrift German Pat. No. 1 264 120 which are kept in their initial position against the force of a spring by means of a holding magnet. Upon release of the print hammer, this magnet is correspondingly energized, so that its holding force is no longer maintained, and the print hammer is driven by the biased spring.
However, all such holding systems are not free from contacts, i.e., the disadvantages these entail, such as contact bounces and wear, have to be tolerated, or additional measures have to be taken to avoid them.